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. 2020 Dec 17;10(73):44699-44711.
doi: 10.1039/d0ra08783a.

A new synthetic route for the preparation of [Os3(CO)10(μ-OH)(μ-H)] and its reaction with bis(diphenylphosphino)methane (dppm): syntheses and X-ray structures of two isomers of [Os3(CO)8(μ-OH)(μ-H)(μ-dppm)] and [Os3(CO)7(μ3-CO)(μ3-O)(μ-dppm)]

Md Tuhinur R Joy  1 , Nikhil C Bhoumik  1 , Shishir Ghosh  1 , Michael G Richmond  2 , Shariff E Kabir  1
Affiliations

A new synthetic route for the preparation of [Os3(CO)10(μ-OH)(μ-H)] and its reaction with bis(diphenylphosphino)methane (dppm): syntheses and X-ray structures of two isomers of [Os3(CO)8(μ-OH)(μ-H)(μ-dppm)] and [Os3(CO)7(μ3-CO)(μ3-O)(μ-dppm)]

Md Tuhinur R Joy et al. RSC Adv. .

Abstract

The triosmium cluster [Os3(CO)10(μ-OH)(μ-H)] containing bridging hydride and hydroxyl groups at a common Os-Os edge was obtained in good yield (ca. 75%) from the hydrolysis of the labile triosmium cluster [Os3(CO)10(NCMe)2] in THF at 67 °C. [Os3(CO)10(μ-OH)(μ-H)] reacts with dppm at 68 °C to afford the isomeric clusters 1 and 2 with the general formula [Os3(CO)8(μ-OH)(μ-H)(μ-dppm)] that differ by the disposition of bridging dppm ligand. Cluster 1 is produced exclusively from the reaction of [Os3(CO)10(μ-OH)(μ-H)] with dppm in CH2Cl2 at room temperature in the presence of added Me3NO. Heating cluster 1 at 81 °C furnishes 2 in a process that likely proceeds by the release of one arm of the dppm ligand, followed by ligand reorganization about the cluster polyhedron and ring closure of the pendent dppm ligand. The oxo-capped [Os3(CO)7(μ3-CO)(μ3-O)(μ-dppm)] (3) has been isolated starting from the thermolysis of either 1 or 2 at 139 °C. Reactions of [Os3(CO)10(μ-dppm)] with ROH (R = Me, Et) in the presence of Me3NO at 80 °C furnish [Os3(CO)8(μ-OH)(μ,η1,κ1-OCOR)(μ-dppm)] (4, R = Me; 5, R = Et). Clusters 1-5 have been characterized by a combination of analytical and spectroscopic studies, and the molecular structure of each product has been established by X-ray crystallography. The bonding in these products has been examined by electronic structure calculations, and cluster 1 is confirmed as the kinetic product of substitution, while cluster 2 represents the thermodynamically favored isomer.

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Conflict of interest statement

There are no conflicts to declare.

Figures

Scheme 1
Scheme 1. Synthesis of [Os3(CO)10(μ-OH)(μ-H)].
Scheme 2
Scheme 2. Cis and trans stereoisomers for [Os3(CO)10(μ-OH)(μ-H)].
Fig. 1
Fig. 1. DFT-optimized structures of the trans (A1) and cis (A2) isomers of [Os3(CO)10(μ-OH)(μ-H)] and the free-energy surface for pyramidal inversion viaTSA1A2. Energy values are ΔG in kcal mol−1 relative to A1.
Scheme 3
Scheme 3. Reaction of [Os3(CO)10(μ-OH)(μ-H)] with dppm.
Scheme 4
Scheme 4. Interconversion of 1 and 2 and their transformation paths to 3.
Fig. 2
Fig. 2. Molecular structure of [Os3(CO)8(μ-OH)(μ-H)(μ-dppm)] (1, left) and DFT-optimized structure B1 (right). The atomic displacement ellipsoids are shown at the 50% probability and the hydrogen atoms (except for the hydride and hydroxyl proton) are omitted for clarity. Selected bond lengths (Å) and bond angles (°) for the experimental structure: Os(1)–Os(2) 2.77027(18), Os(1)–Os(3) 2.82141(18), Os(2)–Os(3) 2.85356(18), Os(1)–P(1) 2.3350(7), Os(2)–P(2) 2.3589(8), Os(1)–O(9) 2.149(2), Os(2)–O(9) 2.144(2), P(1)–Os(1)–Os(2) 94.627(19), P(1)–Os(1)–Os(3) 155.817(19), P(1)–Os(1)–O(9) 80.38(6), O(9)–Os(1)–Os(2) 49.73(6), O(9)–Os(1)–Os(3) 85.24(6), Os(1)–O(9)–Os(2) 80.37(8), Os(3)–O(9)–H(9) 79.03(3).
Fig. 3
Fig. 3. Optimization and energy ordering for the isomeric clusters based on 1 (top) and important van der Waals contacts in B2 involving the hydroxyl hydrogen and the dppm ligand (bottom). The energy difference (ΔG) on the upper potential energy surface is relative to B1 in kcal mol−1 and is not drawn to scale. The ancillary CO ligands and distal phenyl groups in the bottom representation of B2 have been omitted for clarity.
Fig. 4
Fig. 4. Molecular structure of [Os3(CO)8(μ-OH)(μ-H)(μ-dppm)] (2) showing 50% probability atomic displacement ellipsoids. Hydrogen atoms (except the hydride) are omitted for clarity. Selected bond lengths (Å) and bond angles (°): Os(1)–Os(2) 2.830(2), Os(1)–Os(3) 2.8079(17), Os(2)–Os(3) 2.7896(17), Os(1)–P(1) 2.326(3), Os(2)–P(2) 2.305(3), Os(2)–O(9) 2.147(6), Os(3)–O(9) 2.144(6), P(1)–Os(1)–Os(2) 94.93(6), P(1)–Os(1)–Os(3) 153.52(6), P(2)–Os(2)–Os(1) 86.69(6), P(2)–Os(2)–Os(3) 134.27(7), P(2)–Os(2)–O(9) 97.54(18), O(9)–Os(2)–Os(3) 49.41(16), O(9)–Os(2)–Os(1) 79.42(15), Os(2)–O(9)–Os(3) 81.1(2).
Fig. 5
Fig. 5. DFT-optimized structures of C2 (left) and C1 (right) based on the minor product isolated from the reaction of [Os3(CO)10(μ-OH)(μ-H)] and dppm.
Scheme 5
Scheme 5. Alternative isomers for cluster 2.
Fig. 6
Fig. 6. Molecular structure of [Os3(CO)7(μ3-CO)(μ3-O)(μ-dppm)] (3, left) and DFT-optimized structure D (right). The atomic displacement ellipsoids are shown at the 50% probability and the hydrogen atoms are omitted for clarity. Selected bond lengths (Å) and bond angles (°) for the experimental structure: Os(1)–Os(2) 2.7754(11), Os(1)–Os(3) 2.7583(11), Os(2)–Os(3) 2.7472(8), Os(1)–P(1) 2.3301(13), Os(2)–P(2) 2.3233(13), Os(1)–O(9) 2.087(3),Os(2)–O(9) 2.088(3), Os(3)–O(9) 2.069(3), Os(1)–C(8) 2.143(4), Os(2)–C(8) 2.147(4), Os(3)–C(8) 2.231(4), P(1)–Os(1)–Os(2) 92.72(3), P(1)–Os(1)–Os(3) 144.24(3), P(1)–Os(1)–O(9) 97.03(8), O(9)–Os(1)–Os(2) 48.34(7), Os(1)–O(9)–Os(2) 83.33(10), C(8)–Os(1)–Os(2) 49.76(10), Os(1)–C(8)–Os(2) 80.63(14).
Scheme 6
Scheme 6. Synthesis of hydroxyl-bridged clusters [Os3(CO)8(μ-OH)(μ,η1,κ1-OCOR)(μ-dppm)].
Scheme 7
Scheme 7. Potential source of alkoxide anion from Me3NO and alcohol.
Fig. 7
Fig. 7. Molecular structure of [Os3(CO)8(μ-OH)(μ,η1,κ1-OCOMe)(μ-dppm)] (4) showing 50% probability atomic displacement ellipsoids. Hydrogen atoms are omitted for clarity. Selected bond lengths (Å) and bond angles (°): Os(1)–Os(2) 2.8772(3), Os(1)–Os(3) 2.8762(3), Os(1)–P(1) 2.3201(14), Os(2)–P(2) 2.2957(14), Os(2)–O(9) 2.121(4), Os(3)–O(9) 2.115(4), Os(2)–O(10) 2.145(4), Os(3)–C(9) 2.083(6), Os(2)–Os(1)–Os(3) 71.926(9), Os(2)–O(9)–Os(3) 105.84(18), P(1)–Os(1)–Os(2) 92.23(4), P(1)–Os(1)–Os(3) 164.03(4), O(9)–Os(2)–Os(1) 80.54(11), O(10)–Os(2)–O(9) 81.73(16), O(10)–Os(2)–Os(1) 87.94(11), C(9)–Os(3)–O(9) 82.2(2), C(9)–Os(3)–Os(1) 87.24(16).
Fig. 8
Fig. 8. Molecular structure of [Os3(CO)8(μ-OH)(μ,η1,κ1-OCOEt)(μ-dppm)] (5) and DFT-optimized structure E (right). The atomic displacement ellipsoids are shown at the 50% probability and the hydrogen atoms (except for the hydroxyl proton) are omitted for clarity. Selected bond lengths (Å) and bond angles (°) for the experimental structure: Os(1)–Os(2) 2.8683(3), Os(1)–Os(3) 2.8716(3), Os(1)–P(1) 2.3204(9), Os(2)–P(2) 2.2993(9), Os(2)–O(9) 2.113(3), Os(3)–O(9) 2.107(3), Os(2)–O(10) 2.148(2), Os(3)–C(9) 2.073(4), Os(2)–Os(1)–Os(3) 71.906(6), Os(2)–O(9)–Os(3) 105.98(12), P(1)–Os(1)–Os(2) 90.82(2), P(1)–Os(1)–Os(3) 162.73(2), O(9)–Os(2)–Os(1) 79.63(8), O(10)–Os(2)–O(9) 82.22(10), O(10)–Os(2)–Os(1) 89.00(6), C(9)–Os(3)–O(9) 82.35(12), C(9)–Os(3)–Os(1) 87.53(10).
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